This invention relates to occupancy sensors. More particularly, this invention relates to occupancy sensors that provide long-range occupancy sensing within a narrow field of view.
Occupancy sensors typically sense the presence of one or more persons within a designated area and generate occupancy signals indicative of that presence. These signals activate or deactivate one or more electrical appliances, such as, for example, a lighting unit or a heating, ventilating, and air conditioning system. Occupancy sensors help reduce maintenance and electrical energy costs by indicating when these appliances can be turned off.
Conventional occupancy sensors sense occupancy by projecting a detecting beam, (active sensing) or defining a detection zone (passive sensing), through a curved lens that provides the sensor with a wide field of view. This field of view typically ranges from about 160.degree. for wall-mounted sensors to about 360.degree. for ceiling-mounting sensors. Occupancy os sensed, for example, when the the heat differential between the background heat of the designated area and that of a person entering the area is sensed.
Such conventional occupancy sensors, however, are typically inefficient when used in environments requiring long-range, narrow field of view sensing, such as in warehouse environments. Warehouse environments typically have long aisles between high storage areas. Accordingly, much of the energy used to generate detecting beams or define detection zones in wide fields of view is wasted, rendering conventional sensors inefficient. Moreover, the curved lenses used to provide the wide fields of view limit the sensing range of conventional sensors. Thus, each aisle may typically require several conventional occupancy sensors to provide adequate coverage. This alone may render conventional occupancy sensors impractical in large warehouse environments having hundreds of thousands of square feet.
Furthermore, warehouse environments typically have high ceilings (e.g., 30 feet). To provide the proper angles for optimum sensing performance, occupancy sensors should preferably be mounted on walls near the top. Scissor lifts are usually required to install occupancy sensors at that height. The occupancy sensors are thus not easily accessible. Adjustments and final alignments can therefore be very difficult and time consuming. For example, it is often difficult to determine if a conventional sensor is positioned properly for sensing occupancy down a long aisle. The light emitting diode commonly used in conventional sensors to signal occupancy cannot normally be seen when attempting to locate the long-range sensing limit of the sensor.
Warehouse environments frequently contain dust and other airborne particles that can adversely affect the operation of conventional occupancy sensors, which generally are not adequately protected from such conditions. The large curved lens areas of conventional sensors require regular periodic cleaning, and the sensor electronics often become contaminated requiring cleaning or replacement. Conventional occupancy sensors are thus subject to increased maintenance, which is made more difficult because of their high mount location.
Also, warehouse environments commonly use high intensity discharge (HID) lighting. This type of lighting typically operates at two settings: high intensity and low intensity. When power is first applied, HID lamps usually require a warm-up period at high intensity of about 15 to 20 minutes. Thus, these lamps are not regularly turned off. When used with occupancy sensors, an HID lamp operates at high intensity when a signal indicating occupancy is received and at low intensity when a signal indicating non-occupancy is received. Furthermore, when HID lamps are first installed, they require operation at high intensity for about 100 hours or more (i.e., a burn-in period) in order to reach their true color rendition. Conventional occupancy sensors are not well-suited for HID lighting.
Conventional occupancy sensors typically do not automatically operate in occupancy mode (i.e., the sensor outputs a signal indicating occupancy) for a fixed period of time when the sensor first powers-up. Some occupancy sensors do however have a manual override switch that sets the sensor in occupancy mode. Thus, to operate HID lamps at high intensity for the warm-up period when first powered-up, conventional occupancy sensors have to be manually set in occupancy mode for the warm-up period, and then manually reset to normal operation. In a warehouse environment with hundreds or thousands of HID lamps, such a manual effort is impractical at best and prohibitively time consuming and costly at worst.
Similarly, to provide a burn-in period for newly installed HID lamps, conventional occupancy sensors should also be manually set to occupancy mode, and then manually reset to normal operation after the burn-in period. Again, such a manual effort is impractical at best and prohibitively time consuming and costly at worst.
In view of the foregoing, it would be desirable to provide an occupancy sensor that provides more efficient long-range occupancy sensing within a narrow field of view.
It would also be desirable to provide an occupancy sensor that can be easily adjusted and aligned to sense occupancy within a designated area.
It would further be desirable to provide an occupancy sensor that can be set in occupancy mode for a predetermined time period, after which the sensor automatically returns to normal operation.
It would still further be desirable to provide an occupancy sensor that upon power-up automatically operates in occupancy mode for a predetermined warm-up period, after which the sensor automatically returns to normal operation.